The present invention relates to the annealing of a newly formed glass ribbon and particularly relates to a method and apparatus for sensing the temperature at a critical portion of the cooling cycle at which the ease of cutting the ribbon and the likelihood of glass breakage is determined. The present invention is particularly useful to monitor the temperature of a moving ribbon of float glass in the region of the ribbon that is usually trimmed from the ribbon to produce blanks of commercially acceptable glass from the ribbon.
In the past, glass surface temperature measurements during annealing have been performed by thermocouples or temperature sensing elements spaced from the glass surface. Using temperature sensing elements spaced from the glass surface avoided scratching of the glass surfaces. However, other problems such as the sensing of extraneous radiation not associated with the temperature of the glass being monitored tended to cause errors in the sensed temperature.
Typical examples of patents providing non-contacting temperature sensing devices for moving glass ribbons are U.S. Pat. No. 2,912,862 to Machler et al and U.S. Pat. No. 3,600,947 to Farabaugh.
U.S. Pat. No. 3,500,548 to Mitsuno discloses the use of a pair of graphite electrodes positioned within a ribbon forming apparatus and adapted to contact the edge portion of a newly formed ribbon for the purpose of determining the presence or absence of the edge at an inspection station in a method of detecting and measuring the width of the ribbon as it passes the detection station. When the ribbon is narrower than the range of width to be detected, the electrodes do not contact any glass ribbon. When the ribbon width is greater, an edge portion of the ribbon is in contact with one or both of the electrodes mounted for contact by the ribbon edge portion. However, the edge detection apparatus of the Mitsuno patent is not used for determination of temperature at the ribbon edge.